multi level inheritance in c++

//multi level inheritance
#include <iostream.h>
#include <conio.h>

class A
{
protected:
    int a;
public:

        A()
    {
    cout<<"constructor A executed"<<endl;
    }

        void input()
    {
    cout<<"enter a ";
    cin>>a;
    }

        void output()
    {
    cout<<a<<endl;
    }
};


class B:public A
{
public:

        B()
    {
    cout<<"constructor B executed"<<endl;
    }
};


class C:public B
{
public:
        C()
    {
    cout<<"constructor C executed"<<endl;
    }
};


        void main()
    {
    C obj;
    obj.input();
    obj.output();
   getch();
   }